The Present Disclosure relates generally to high speed data transmission systems suitable for use in transmitting high speed signals at low losses from chips, or processors and the like to backplanes, mother boards and other circuit boards, and more particularly to a bypass cable assembly having connectors that provide reliable wiping action during connection to circuit boards contacts of an electronic component.
Electronic devices such as routers, servers, switches and the like need to operate at high data transmission speeds in order to serve the rising need for bandwidth and delivery of streaming audio and video in many end user devices. These devices use signal transmission lines that extend between a primary chip member mounted on a printed circuit board (mother board) of the device, such as an ASIC, FPGA, etc. and connectors mounted to the circuit board. These transmission lines are currently formed as conductive traces on or in the mother board and extend between the chip member(s) to external connectors or circuitry of the device.
Typical circuit boards are usually formed from an inexpensive material known as FR4, which is inexpensive. Although inexpensive, FR4 is known to be lossy in high speed signal transmission lines which transfer data at rates of about 6 Gbps and greater. These losses increase as the speed increases and therefore make FR4 material undesirable for the high speed data transfer applications of about 10 Gbps and greater. This drop off begins at 6 Gbps and increases as the data rate increases. In order to use FR4 as a circuit board material for signal transmission lines, a designer may have to utilize amplifiers and equalizers, which increase the final cost of the device.
The overall length of the signal transmission lines in FR4 circuit boards can exceed threshold lengths, about 10 inches, and may include bends and turns that can create signal reflection and noise problems as well as additional losses. Losses can sometimes be corrected by the use of amplifiers, repeaters and equalizers but these elements also increase the cost of manufacturing the final circuit board. This complicates the layout of the circuit board as additional board space is needed to accommodate these amplifiers and repeaters. In addition, the routing of signal transmission lines in the FR-4 material may require multiple turns. These turns and the transitions which occur at termination points along the signal transmission lines may negatively affect the integrity of the signals transmitted thereby. It then becomes difficult to route transmission line traces in a manner to achieve a consistent impedance and a low signal loss therethrough. Custom materials, such as MEGTRON, are available for circuit board construction which reduces such losses, but the prices of these materials severely increases the cost of the circuit board and, consequently, the electronic devices in which they are used.
Chips are the heart of these routers, switches and other devices. These chips typically include a processor such as an ASIC (application specific integrated circuit) chip and this ASIC chip has a die that is connected to a substrate (its package) by way of conductive solder bumps. The package may include micro-vias or plated through holes which extend through the substrate to solder balls. These solder balls comprise a ball grid array by which the package is attached to the motherboard. The motherboard includes numerous traces formed in it that define transmission lines which include differential signal pairs for the transmission of high speed data signals, ground paths associated with the differential signal pairs, and a variety of low speed transmission lines for power, clock signals and other functions. These traces can include traces routed from the ASIC to the I/O connectors of the device into which external connectors are connected, as well as others that are routed from the ASIC to backplane connectors that permit the device to be connected to an overall system such as a network server or the like or still others that are routed from the ASIC to components and circuitry on the motherboard or another circuit board of the device in which the ASIC is used.
FR4 circuit board materials can handle data transmission speeds of 10 Gbits/sec, but this handling comes with disadvantages. In order to traverse long trace lengths, the power required to transmit these signals also increases. Therefore, designers find it difficult to provide “green” designs for such devices, as low power chips cannot effectively drive signals for such and longer lengths. The higher power needed to drive the signals consumes more electricity and it also generates more heat that must be dissipated. Accordingly, these disadvantages further complicate the use of FR4 as a motherboard material used in electronic devices. Using more expensive, and exotic motherboard materials, such as MEGTRON, to handle the high speed signals at more acceptable losses increases the overall cost of electronic devices. Notwithstanding the low losses experienced with these expensive materials, they still require increased power to transmit their signals and incurred, and the turns and crossovers required in the design of lengthy board traces create areas of signal reflection and potential increased noise.
It therefore becomes difficult to adequately design signal transmission lines in circuit boards and backplanes to meet the crosstalk and loss requirements needed for high speed applications. Although it is desirable to use economical board materials such as FR4, the performance of FR4 falls off dramatically as the data transmission rate approaches 10 Gbps, driving designers to use more expensive board materials and increasing the overall cost of the device in which the circuit board is used. Accordingly, the Present Disclosure is therefore directed to bypass cable assemblies with suitable point-to-point electrical interconnects that cooperatively define high speed transmission lines for transmitting data signals, at 10 Gbps and greater, and which assemblies have low loss characteristics.